JP5542162B2 - Metal mask and method for manufacturing solar cell - Google Patents

Description

  The present invention relates to a metal mask and a method for manufacturing a solar cell.

  Conventionally, as a mask for printing that can supply a sufficient amount of paste to a substrate with uneven surfaces, a metal mask original plate with different opening dimensions is produced by a photolithographic method, and printed wiring is formed on the metal mask original plate by an etching method. There has been proposed a metal mask for printing in which a convex portion that follows a substrate or a module substrate is formed (for example, see Patent Document 1).

  As a substrate having irregularities on the surface, for example, there is a solar cell element. The solar cell element has, for example, a concavo-convex structure of about 10 μm on the front side (light-receiving surface side) in order to increase the light collection rate in a silicon substrate having a thickness of about 200 μm. Further, a silicon nitride film which is an antireflection film is formed on the surface. On the silicon nitride film, a surface electrode that collects photo-electron converted electrons is formed. On the back surface of the silicon substrate, a back surface connection electrode is formed which contacts the back surface electrode and the external electrode.

  In general, the surface electrode is formed by printing a paste-like material on a predetermined position of a silicon substrate by a screen printing method using a screen mask having a transmissive portion of a desired pattern, and performing high-temperature processing in a baking furnace. .

  As an electrode forming method, a screen printing method is currently mainstream as a method that can be manufactured at low cost. For example, a grid electrode (narrow electrode) as a surface electrode is formed using a metal mask having a predetermined pattern in a metal plate without a mesh, and a bus electrode (width) as a surface electrode orthogonal to the grid electrode. There is a method of forming an electrode on the light-receiving surface side by overlapping (multilayer) printing using a screen mask (for example, see Patent Document 2).

  As a previous example using a screen mask, a method of increasing the light receiving area without decreasing the current collection rate by making the shape of the grid electrode thinner with increasing distance from the bus electrode is also shown ( For example, see Patent Document 3).

JP 2008-302567 A Japanese Patent No. 3803133 JP-A-6-283737

  However, in the method of overlapping (multi-layer) printing using a metal mask and a screen mask, there are problems that man-hours increase and production tact decreases. Furthermore, in order to realize a narrow grid electrode without disconnection or printing blur, the use of different print masks for overprinting increases the number of print mask management items (especially pitch variation between wirings), which is even higher. There was a problem related to overlay accuracy. As the grid electrode width becomes narrower, higher overlay accuracy is required and the risk of displacement increases. As a result, there is a problem that the grid electrode width is widened and the yield in the electrode forming process is lowered.

  Therefore, in order to reduce man-hours and improve yield, for example, bus electrodes and grid electrodes are collectively formed with a metal mask, and an off-contact printing method (printing with a predetermined interval between the mask and the substrate) is performed. It is conceivable to adopt a method of

  In this case, an opening for a bus electrode and an opening for a grid electrode are formed in the metal mask. If it does so, the deformation | transformation of the connection part of a bus electrode and a grid electrode will become a problem easily with the force applied at the time of printing. In particular, when printing with the off-contact printing method, the metal mask itself is connected at the connection between the grid electrode and the bus electrode formed at the outermost ends along the tensile direction due to deformation and tensile force applied during repeated printing. There was a problem of being easily damaged.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a metal mask that is not easily damaged even when screen printing by an off-contact printing method is repeated.

  In order to solve the above-described problems and achieve the object, the present invention applies a pressing force from the second surface side, which is the back surface of the first surface, so as to exhibit a plate-like shape and the first surface side is convex. And is formed on the first surface side of the plate-like portion so as to extend along the first direction, and the first of the plate-like portion. A groove formed so as not to reach the end portion along the direction of the groove, a plurality of first openings formed on the bottom surface of the groove and penetrating to the second surface side which is the back surface side of the first surface, and connected to the groove The second opening that extends along the second direction perpendicular to the first direction and penetrates the plate-like portion, and the groove and the second opening of the first surface side of the plate-like portion are formed as described above. It is a region that is closer to the end portion along the first direction than the formed region, and does not overlap with the extension line of the groove along the first direction. A third opening formed in the region, wherein the third opening is formed to extend along the second direction, and has a width of the second opening along the first direction rather than the groove width of the groove. It is characterized by being smaller.

  According to the present invention, there is an effect that the metal mask can be prevented from being damaged by suppressing the deformation at the connection portion between the bus electrode and the grid electrode formed at the outermost both ends. In addition, since electrodes having different widths can be simultaneously formed by one printing, it is possible to perform high-speed printing as compared with the case of performing overprinting, and it is possible to form a surface electrode with a stable shape with little positional deviation. .

FIG. 1-1 is a cross-sectional view illustrating a schematic configuration of a solar cell. FIG. 1-2 is a plan view illustrating a schematic configuration of a solar cell. FIG. 2 is a plan view of the metal mask according to the first embodiment of the present invention. 3 is a cross-sectional view taken along line AA shown in FIG. 4 is a cross-sectional view taken along line BB shown in FIG. FIG. 5 is a cross-sectional view taken along the line CC shown in FIG. FIG. 6 is a schematic diagram for explaining screen printing using the metal mask shown in FIG. FIG. 7 is a diagram showing a printing result when the metal mask shown in FIG. 2 is used for screen printing. FIG. 8 is a flowchart showing a method of screen printing a surface electrode using the metal mask shown in FIG. FIG. 9 is a plan view of a metal mask shown as a comparative example. FIG. 10 is a plan view showing an example of breakage of the metal mask shown in FIG. FIG. 11 is a diagram showing the relationship between the film thickness of the electrode and the line width, and compares the case of using a screen mask and the case of using a metal mask. FIG. 12 is a plan view of a metal mask according to the second embodiment of the present invention. FIG. 13 is a plan view of a metal mask according to the third embodiment of the present invention. 14 is a cross-sectional view taken along line EE shown in FIG. FIG. 15 is a plan view of a metal mask according to the fourth embodiment of the present invention.

  Below, the manufacturing method of the metal mask and solar cell concerning embodiment of this invention is demonstrated in detail based on drawing. Note that the present invention is not limited to the embodiments. In the drawings shown below, the scale of each member may be different from the actual scale for easy understanding. The same applies between the drawings. Further, in order to make the drawing easy to see, hatching may be given even in a plan view, and hatching may be omitted even in a cross-sectional view.

Embodiment 1 FIG.
First, a schematic configuration of a solar cell manufactured using the metal mask according to the first embodiment of the present invention will be described. FIG. 1-1 is a cross-sectional view illustrating a schematic configuration of a solar cell. FIG. 1-2 is a plan view illustrating a schematic configuration of a solar cell.

  The solar cell 50 includes a P-type semiconductor substrate 21 that is a first conductivity-type semiconductor substrate having an N layer 21a that is an impurity diffusion layer in which a second conductivity-type impurity element is diffused in the surface layer of the substrate, and light reception by the semiconductor substrate 21. The antireflection film 22 formed on the surface (surface) on the surface 25 side, the surface electrode 23 formed on the surface on the light receiving surface 25 side of the semiconductor substrate 21, and the surface (back surface) opposite to the light receiving surface of the semiconductor substrate 21 ) Formed on the back electrode 24. Note that an N-type semiconductor substrate may include a P layer.

  Moreover, as the surface electrode 23, the grid electrode 23a and the bus electrode 23b are included, In FIG. 1-1, sectional drawing in the cross section perpendicular | vertical to the longitudinal direction of the grid electrode 23a is shown. And the solar cell is comprised for the semiconductor substrate 21 using the board | substrate which formed the texture structure in the board | substrate surface.

  Next, the process for manufacturing the solar cell 50 will be described. In addition, since the process demonstrated here is the same as the manufacturing process of the solar cell using a general polycrystalline silicon substrate, it does not show in particular in figure.

  First, a p-type polycrystalline silicon substrate having a thickness of, for example, several hundred μm is prepared as the semiconductor substrate 21 and substrate cleaning is performed. Then, the p-type polycrystalline silicon substrate is immersed in an acid such as hydrofluoric acid or a heated alkaline solution to etch the surface, and is generated near the surface of the p-type polycrystalline silicon substrate when the silicon substrate is cut out. Remove damaged areas. Thereafter, it is washed with pure water.

  Following the removal of the damage, for example, the p-type polycrystalline silicon substrate is immersed in a mixed solution of sodium hydroxide and isopropyl alcohol (IPA), and anisotropic etching is performed on the p-type polycrystalline silicon substrate. A texture structure is formed by forming minute irregularities on the surface of the silicon substrate on the light receiving surface side, for example, with a depth of about 10 μm. By providing such a texture structure on the light-receiving surface side of the p-type polycrystalline silicon substrate, multiple reflection of light is caused on the surface side of the solar cell, and light incident on the solar cell is efficiently transmitted to the inside of the semiconductor substrate 21. Therefore, it is possible to effectively reduce the reflectivity and improve the conversion efficiency.

Next, the p-type polycrystalline silicon substrate having a textured structure is put into a thermal oxidation furnace and heated in the presence of phosphorus oxychloride (POCl ₃ ) vapor to form phosphorus glass on the surface of the p-type polycrystalline silicon substrate. As a result, phosphorus is diffused into the p-type polycrystalline silicon substrate, and an N layer 21a is formed on the surface layer of the p-type polycrystalline silicon substrate. Thereby, the semiconductor substrate 21 having the N layer 21a on the substrate surface layer is obtained.

  Next, after removing the phosphor glass layer of the semiconductor substrate 21 in a hydrofluoric acid solution, a SiN film is formed as an antireflection film 22 on the N layer 21a except for the formation region of the surface electrode 23 by plasma CVD. The film thickness and refractive index of the antireflection film are set to values that most suppress light reflection. Note that two or more layers having different refractive indexes may be stacked. The antireflection film 22 may be formed by a different film forming method such as a sputtering method.

  Next, a paste material (electrode material) mixed with silver is printed on the light receiving surface 25 of the semiconductor substrate 21 in a comb shape by screen printing, and a paste mixed with aluminum is printed on the entire back surface of the semiconductor substrate 21 by screen printing. After printing, a baking process is performed to form the front electrode 23 and the back electrode 24. As described above, the solar cell 50 shown in FIGS. 1-1 and 1-2 is manufactured.

  FIG. 2 is a plan view of the metal mask according to the first embodiment of the present invention. 3 is a cross-sectional view taken along line AA shown in FIG. 4 is a cross-sectional view taken along line BB shown in FIG. FIG. 5 is a cross-sectional view taken along the line CC shown in FIG. In FIG. 2, the metal mask 10 is viewed from the front surface (first surface) 11a side. The metal mask 10 is a mask used for screen printing when the surface electrode 23 is formed on the light receiving surface 25 in the manufacturing process of the solar cell 50 described above.

  FIG. 6 is a schematic view for explaining screen printing using the metal mask 10 shown in FIG. In the formation of the surface electrode 23, the metal mask 10 is disposed so that the surface 11 a of the plate-like portion 11 faces the light receiving surface 25 of the semiconductor substrate 21, which is a printed material, with both ends being held by the plate frame 4. The The paste material is pushed by the squeegee rubber 1 from the back surface 11b side of the plate-like portion 11 so that the paste material passes through the through-hole formed so as to penetrate the metal mask 10 (plate-like portion 11). Printed in position.

  In the present embodiment, an example of off-contact printing in which screen printing is performed in a state where a predetermined interval (for example, an interval of 1.5 mm to 2 mm) is provided between the metal mask 10 and the substrate. During screen printing, the squeegee rubber 1 is pressed against the back surface 11b side of the metal mask 10, so that a pressing force is applied from the back surface 11b side of the plate-like portion 11, and the plate-like portion 11 is deformed so that the front surface 11a side is convex. . Accordingly, a tensile force is applied to the metal mask 10 in the direction indicated by the arrow X. By performing off-contact printing, the metal mask 10 is easily deformed at both ends along a direction in which a tensile force is applied (hereinafter also referred to as a first direction).

  The metal mask 10 includes a plate-like portion 11 having a plate-like shape. In the plate-like portion 11, the groove 30 and the first opening 31 for forming the grid electrode 23a, the second opening 32 for forming the bus electrode 23b, and the damage of the metal mask 10 due to the tensile force applied at the time of screen printing. A dummy opening (third opening) 33 for suppression is formed.

  The groove 30 is formed on the surface 11a so as to extend along the first direction (the direction indicated by the arrow X, see also FIG. 2). Moreover, the groove | channel 30 is formed in the length which does not reach the edge part hold | maintained at the plate frame 4 among the edge parts of the plate-shaped part 11, ie, the edge part along a 1st direction. Further, the groove 30 is formed in a plane shape substantially the same as the plane shape of the bus electrode 23b. A plurality of first openings 31 are formed on the bottom surface of the groove 30. As shown in FIGS. 3 and 4, the first opening 31 is formed so as to penetrate from the bottom surface of the groove 30 to the back surface 11 b of the plate-like portion 11. Therefore, at the time of screen printing, the paste material pushed from the back surface 11 b of the plate-like portion 11 enters the groove 30 through the first opening 31, and is extruded through the groove 30 to the front surface 11 a side. A bus electrode 23 b that follows the planar shape of the groove 30 is printed on the light receiving surface 25 of the semiconductor substrate 21.

  As shown in FIG. 2, the second opening 32 is formed so as to extend along a second direction perpendicular to the first direction (the direction indicated by the arrow Y, see also FIG. 2). The second opening 32 is formed in a shape substantially the same as the planar shape of the grid electrode 23a. As shown in FIG. 4, the second opening 32 is formed so as to be connected to the groove 30, and is an open opening penetrating from the front surface 11 a to the back surface 11 b of the plate-like portion 11. Therefore, at the time of screen printing, the paste material pushed from the back surface 11 b of the plate-like portion 11 is extruded to the front surface 11 a side through the second opening 32. Then, a grid electrode 23 a following the planar shape of the second opening is printed on the light receiving surface 25 of the semiconductor substrate 21.

  Of the second openings 32, the grooves 30 and the second openings 32 are located closer to the ends than the second openings 32 (the end openings 32 a shown in FIG. 2) formed closest to the ends along the first direction. One opening 31 (the endmost opening 31a shown in FIG. 2) is formed.

  Of the plate-like portion 11, the region where the groove 30, the first opening 31 and the second opening 32 are formed, that is, the region for printing the grid electrode 23 a and the bus electrode 23 b (print region P) is the first. A dummy opening (third opening) 33 is formed in a region (dummy region Q) on the end side of the plate-like portion 11 along the direction of. The dummy opening 33 includes a plurality of through holes 33 a to 33 c that penetrate from the front surface 11 a to the back surface 11 b of the plate-like portion 11.

  The through holes 33a to 33c are arranged along the second direction, and the dummy opening 33 is formed so as to extend along the second direction as a whole. For example, in FIG. 2, it is assumed that the through holes 33 a to 33 c have a width of 60 μm, and the through holes 33 a to 33 c are arranged with a width of 40 μm in the second direction. Moreover, the area | region (bridge | crosslinking pattern 34) pinched | interposed between through-holes 33a-33c is made thinner than the thickness of the other area | region of the plate-shaped part 11, for example, the thickness of the metal mask 10 is 70 micrometers in FIG. In this case, it is assumed that the thickness of the cross-linking pattern 34 is 40 μm. Moreover, it is assumed that the bridging patterns 34 are provided at a pitch of 200 μm. The dummy opening 33 is formed in a region that does not overlap with the extension line of the groove 30, that is, a region that is out of the region sandwiched between two-dot chain lines in FIG.

  FIG. 7 is a diagram showing a printing result when the metal mask 10 shown in FIG. 2 is used for screen printing. When screen printing is performed using the metal mask 10, a printing result as shown in FIG. 7 is obtained. Of the printed paste material, the paste material 51 printed through the dummy opening 33 cannot be used as the grid electrode 23a or the bus electrode 23b, and therefore an unnecessary printing result is obtained. Therefore, as shown in FIG. 6, screen printing is performed after a film (dummy film 52) is inserted between the light receiving surface 25 of the semiconductor substrate 21 and the dummy region Q of the metal mask 10. Since the paste material that has passed through the dummy opening 33 is printed on the dummy film 52, unnecessary paste material can be easily removed from the light receiving surface 25 of the semiconductor substrate 21 by removing the dummy film 52 after completion of screen printing.

  FIG. 8 is a flowchart showing a method for screen printing the surface electrode 23 using the metal mask 10 shown in FIG. First, the metal mask 10 is arranged so that the surface 11a faces the light receiving surface 25 of the semiconductor substrate 21 with a predetermined interval (step S1) (see also FIG. 6). Next, the dummy film 52 is disposed between the dummy area Q and the light receiving surface 25 (step S2). The dummy film 52 only needs to be disposed at least between the dummy opening 33 and the light receiving surface 25.

  Next, a paste-like electrode material is pressed against the back surface 11b side of the metal mask 10 using the squeegee rubber 1 (step S3). As a result, the paste-like electrode material is supplied to the light receiving surface 25 through the groove 30, the first opening 31, the second opening 32, and the dummy opening 33. And the surface electrode 23 is formed in the light-receiving surface 25 by removing the dummy film 52 (step S4). This screen printing process is incorporated into the manufacturing process of the solar cell 50.

  Next, a metal mask 100 as a comparative example will be described. FIG. 9 is a plan view of a metal mask 100 shown as a comparative example. As shown in FIG. 9, the dummy opening 33 (see also FIG. 2) is not formed in the metal mask 100. Further, in the second opening 32, the first opening is further closer to the end than the second opening 32 (the endmost opening 32a shown in FIG. 2) formed closest to the end along the first direction. 31 is not formed.

  As described above, the end portion of the metal mask is deformed by performing the off-contact printing. In particular, the deformation tends to concentrate on the connection portion between the second opening 32 formed at the outermost end along the first direction and the groove 30. Therefore, when the printing process is repeated, the metal mask 100 is easily damaged at the opening position of the outermost end that is most susceptible to deformation in the metal mask 100.

  FIG. 10 is a plan view showing an example of breakage of the metal mask 100 shown in FIG. As shown in FIG. 10, the second opening 32 formed at the outermost end is easily broken at the portion connected to the groove 30. For example, the diameter of the first openings 31 is 100 μm, and the distance between the first openings 31 is 40 μm.

  When the second opening 32 at the outermost end of the metal mask 100 is broken at the portion connected to the groove 30, the width of the second opening 32 at the outermost end is widened. Further, since the width of the second opening 32 at the outermost end is widened, the width of the second opening 32 adjacent to the second opening 32 is narrowed.

  When off-contact printing is performed using the metal mask 100 that has been broken in this way, sufficient paste material cannot pass through the second opening 32 having a reduced width, and the grid electrode 23a (see also FIG. 2) is broken. May occur.

  On the other hand, in the metal mask 10 according to the present embodiment, the dummy opening 33 is formed in the dummy region Q that is on the end side of the printing region P in which the groove 30, the first opening 32, and the second opening 32 are formed. Yes. By forming the dummy opening 33, the deformation of the plate-like portion 11 is dispersed also in the dummy region Q. Therefore, the deformation at the time of screen printing at the broken portion of the metal mask 100 shown in the comparative example is alleviated, and the metal mask 10 is hardly damaged during off-contact printing.

  Further, in the metal mask 100 shown in the comparative example, the second opening 32 is further closer than the second opening 32 (the endmost opening 32a shown in FIG. 2) formed closest to the end along the first direction. Near the end, the first opening 31 is not formed. Therefore, the number of the first openings 31 formed around the connection portion with the groove 30 is reduced as compared with the second openings 32 other than the endmost opening 32a.

  By reducing the number of first openings 31 formed in the periphery, the paste material is not sufficiently supplied at the connection portion with the groove 30 in the endmost opening 32a, and the connection between the grid electrode 23a and the bus electrode 23b is performed. In some cases, the condition became unstable and the wire was broken.

  On the other hand, in the present embodiment, as shown in FIG. 2, the groove 30 and the endmost opening 31a are formed closer to the end than the endmost opening 32a. Therefore, substantially the same number of first openings 31 as the other second openings 32 are formed around the outermost opening 32a.

  And since paste material is supplied also from the end opening 31a with respect to the connection part with the groove | channel 30 among the end openings 32a, supply of paste material is hard to be insufficient, and the grid electrode 23a and the bus electrode 23b The connection state is easy to stabilize. Thereby, disconnection of the grid electrode 23a and the bus electrode 23b can be suppressed.

  In addition, since the second opening 32 of the metal mask 10 is free of obstacles (eg, wrinkles) as seen in a screen mask, it is possible to print the grid electrode 23a having a uniform film thickness (small undulation). The shape of the pattern formed for reference is shown. When a screen mask having an opening width for forming the grid electrode 23a of 60 μm and a mask thickness of 70 μm is used, the printed grid electrode 23a has a thickness of 20 μm. It became 120 μm. On the other hand, when the metal mask 10 having the opening width of the second opening 32 of 60 μm and the mask thickness of 70 μm is used, the thickness of the printed grid electrode 23a is changed from 28 μm to 38 μm, and the film thickness variation is based on the screen mask. It was possible to print and form the grid electrode 23a with less film thickness waviness, which is 1/10 that of the conventional case. The width of the grid electrode 23a was finished to an average width of about 80 μm.

  In addition, the opening width of the second opening 32 may be reduced in order to make the grid electrode 23a thinner. Here, when the opening width for the grid electrode 23a is smaller than 50 μm in the screen mask, the transferability of the paste material to the printed material (semiconductor substrate 21) is lowered due to the presence of wrinkles, and the grid electrode 23a is disconnected. It becomes easy. On the other hand, in the metal mask 10, even if the width of the second opening 32 is 40 μm, since there is no wrinkle, the transferability of the paste material is unlikely to deteriorate, and disconnection is unlikely to occur in the grid electrode 23 a.

  FIG. 11 is a diagram showing the relationship between the film thickness of the electrode and the line width, and is a diagram comparing the case of using the screen mask and the case of using the metal mask 10. In FIG. 11, the line width and film thickness data of the grid electrode 23a formed with a commonly used screen mask and the line width and film thickness data of the grid electrode 23a formed with the metal mask 10 are plotted. . A straight line 35 shown in FIG. 11 indicates a case where the aspect ratio, which is a value obtained by dividing the film thickness by the line width, is 0.5. Data above the line 35 indicates that the aspect ratio is greater than 0.5. Here, the thickness of each mask is set to 70 μm, and the test is performed using the same paste-like material (Ag paste).

  Here, an electrode in which an aspect ratio of an electrode formed by one printing is larger than 0.5 is defined as a high aspect wiring in this embodiment. As shown in FIG. 11, an electrode formed using a general screen mask has an aspect ratio smaller than 0.4, whereas an electrode formed using the metal mask 10 has an aspect ratio of 0.5. Larger and higher aspect wiring can be formed.

  Further, since the metal mask 10 according to the present embodiment can be printed by the off-contact printing method, there is no restriction on the processing time required for the plate separation mechanism, which is a problem in the contact printing method, due to the plate separation operation at the time of printing. The printing process can be speeded up. In the printing press used this time, the processing time related to the plate separation operation required for contact printing when using a conventional metal mask can be reduced to zero by acting as a result of off-contact printing.

  As described above, the metal mask 10 in which the groove 30, the first opening 31, the second opening 32, and the dummy opening 33 are formed is a grid of the solar cell 50 that forms an electrode pattern on a substrate having an uneven structure called a texture. It is suitable for forming the electrode 23a. By using the metal mask 10, the grid electrode 23a can be formed into a thin and thick film with a reduced width, so that the area of the surface electrode 23 that blocks incident light from sunlight can be made as small as possible. Thereby, the fall of the power generation efficiency in the solar cell 50 can be suppressed. In the present embodiment, as an application example of pattern formation using a metal mask, the formation of the surface electrode 23 on the solar cell 50 has been described as an example, but the present invention is not limited to this. That is, it can be widely applied when a pattern is formed on a substrate having an uneven surface.

Embodiment 2. FIG.
FIG. 12 is a plan view of a metal mask according to the second embodiment of the present invention. In addition, about the structure similar to the said embodiment, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted. In the metal mask 60 according to the second embodiment, the dummy openings 63 formed across the extension line of the groove 30 are formed so as to be shifted from each other in the first direction. The dummy opening 63 is formed by arranging a plurality of through holes 63a to 63c, and the bridging pattern 64 is provided between the through holes 63a to 63c, as in the first embodiment, and the through hole 63a. The same applies to the distance between the lines 63c and the like, and the cross-sectional view along the line DD shown in FIG. 12 is the same as FIG.

  Although the arrangement of the dummy grid electrode pattern is not particularly limited, in the present embodiment, the pattern corresponding to the bus electrode is arranged so that the pattern corresponding to the grid electrode does not intersect with the part corresponding to the bus electrode. The connection part between the grid electrode and the bus electrode at the outermost end is the weakest part at the time of off-contact printing. Only the outermost grid electrode has lost the connection with the bus electrode, thereby eliminating the weak points.

  Even when the dummy opening 63 is formed in this way, as in the first embodiment, the deformation at the time of screen printing at the broken portion of the metal mask 100 (see also FIGS. 9 and 10) shown in the comparative example is also achieved. The metal mask 60 is less likely to be damaged.

  In addition, since the second opening 32 of the metal mask 60 is free of obstacles (eg, wrinkles) as seen in a screen mask, it is possible to print the grid electrode 23a having a uniform film thickness (small undulation).

  In addition, since the metal mask 60 according to the second embodiment can be printed by the off-contact printing method, a plate separation operation is accompanied at the time of printing, so that there is a restriction on processing time for the plate separation mechanism which is a problem in the contact printing method. The printing process can be speeded up.

Embodiment 3 FIG.
FIG. 13 is a plan view of a metal mask according to the third embodiment of the present invention. 14 is a cross-sectional view taken along line EE shown in FIG. In addition, about the structure similar to the said embodiment, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted. In the metal mask 70 according to the third embodiment, a dummy opening 73 is formed as a groove having a bottom surface as shown in FIG. For this reason, the paste material does not pass through the dummy openings 73 during screen printing, and the dummy film 52 does not have to be used when forming the surface electrode 23. Therefore, it is possible to reduce the man-hours and further increase the speed of the printing process.

  Further, even when the dummy opening 73 is formed in this way, as in the first embodiment, when the screen printing is performed at the broken portion of the metal mask 100 (see also FIGS. 9 and 10) shown in the comparative example. The deformation is alleviated and the metal mask 70 is less likely to be damaged.

  In addition, since the second opening 32 of the metal mask 70 does not have an obstruction (soot) as seen in the screen mask, it is possible to print the grid electrode 23a having a uniform film thickness (small undulation).

  In addition, since the metal mask 70 according to the third embodiment can be printed by the off-contact printing method, the plate separation operation is accompanied at the time of printing, so that the processing time of the plate separation mechanism, which is a problem in the contact printing method, is restricted. The printing process can be speeded up.

Embodiment 4 FIG.
FIG. 15 is a plan view of a metal mask according to the fourth embodiment of the present invention. In addition, about the structure similar to the said embodiment, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted. In the metal mask 80 according to the fourth embodiment, a dummy opening 83 is formed as a groove as in the third embodiment, and a dummy opening formed with an extension line of the groove 30 interposed therebetween as in the second embodiment. 83 are formed so as to be shifted from each other in the first direction.

  Since the dummy openings 83 are formed as grooves, the paste material does not pass through the dummy openings 83 during screen printing, and the dummy film 52 does not have to be used when forming the surface electrode 23. Therefore, it is possible to reduce the man-hours and further increase the speed of the printing process.

  Further, even when the dummy opening 83 is formed in this way, as in the first embodiment, when the screen printing is performed at the broken portion of the metal mask 100 shown in the comparative example (see also FIGS. 9 and 10). The deformation is alleviated and the metal mask 80 is less likely to be damaged.

  In addition, since the second opening 32 of the metal mask 80 is free of obstacles (eg, wrinkles) as seen in the screen mask, it is possible to print the grid electrode 23a having a uniform film thickness (small undulation).

  In addition, since the metal mask 80 according to the third embodiment can be printed by the off-contact printing method, a plate separation operation is accompanied at the time of printing, so that there is a restriction on processing time for the plate separation mechanism which is a problem in the contact printing method. The printing process can be speeded up.

  As described above, the metal mask according to the present invention is useful for printing wiring on a solar cell, and is particularly suitable for printing wiring by an off-contact printing method.

DESCRIPTION OF SYMBOLS 1 Squeegee rubber 4 Plate frame 10, 60, 70, 80 Metal mask 11 Plate-shaped part 11a Surface (1st surface)
11b Back side (second side)
DESCRIPTION OF SYMBOLS 21 Semiconductor substrate 21a N layer 22 Antireflection film 23 Front surface electrode 23a Grid electrode 23b Bus electrode 24 Back surface electrode 25 Light-receiving surface 30 Groove 31 1st opening 31a Endmost opening 32 2nd opening 32a Endmost opening 33 Dummy opening (3rd opening) )
33a-33c Through-hole 34 Crosslinking pattern 50 Solar cell 51 Paste material 52 Dummy film 63 Dummy opening (third opening)
63a-63c Through-hole 73,83 Dummy opening (3rd opening)
100 Metal mask P Print area Q Dummy area

Claims (9)

A metal mask used for screen printing,
A plate-like portion having a plate-like shape;
A groove formed on the first surface side of the plate-like portion so as to extend along the first direction, and formed so as not to reach an end portion along the first direction of the plate-like portion; ,
A plurality of first openings formed on the bottom surface of the groove and penetrating to the second surface side which is the back surface side of the first surface;
A second opening formed so as to be connected to the groove and extending along a second direction substantially perpendicular to the first direction and penetrating the plate-like portion;
A third opening formed in a region on the first surface side of the plate-like portion that is closer to the end portion along the first direction than the region in which the groove and the second opening are formed; Prepared,
The third opening is formed to extend along the second direction,
A metal mask characterized in that the width of the second opening along the first direction is smaller than the width of the groove.   The metal mask according to claim 1, wherein the third opening penetrates the second surface.   3. The metal mask according to claim 2, wherein the third opening is configured by forming a plurality of through holes side by side along the second direction.   The metal mask according to claim 1, wherein the inside of the third opening has a groove shape having a bottom surface.   5. The metal mask according to claim 1, wherein the third opening is formed in a region that does not overlap with an extension line of the groove along the first direction. The third opening is formed on both sides of the extension line of the groove,
The metal according to any one of claims 1 to 5, wherein the third openings sandwiching the extension line of the groove are formed at positions shifted from each other along the first direction. mask.   2. The first opening is formed closer to the end than the second opening formed closest to the end along the first direction of the plate-like portion. The metal mask as described in any one of -6. A method of manufacturing a solar cell in which a grid electrode and a bus electrode are formed on the light receiving surface side,
Disposing the metal mask according to any one of claims 1 to 7 so that the first surface thereof faces the light receiving surface with a predetermined interval;
Supplying the paste-like electrode material to the light receiving surface through the first to third openings by pressing the second surface side with a squeegee, and
The bus electrode is formed by the electrode material that has passed through the groove and the first opening,
The method for manufacturing a solar cell, wherein the grid electrode is formed of an electrode material that has passed through the second opening. After the step of disposing the metal mask, disposing a dummy film between a third opening of the metal mask and the solar cell;
The method for manufacturing a solar cell according to claim 8, further comprising a step of removing the dummy film after the step of supplying an electrode material to the light receiving surface.

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